import java.util.*;

public class Leet500 {
    public String[] findWords(String[] words) {
        Set<Character> set1 = new HashSet<>(Arrays.asList('q','w','e','r','t','y','u','i','o','p'));
        Set<Character> set2 = new HashSet<>(Arrays.asList('a','s','d','f','g','h','j','k','l'));
        Set<Character> set3 = new HashSet<>(Arrays.asList('z','x','c','v','b','n','m'));
        List<String> list = new ArrayList<>();
        for (String word : words) {
            if (set1.contains(word.charAt(0))){
                for (char c : word.toCharArray()) {
                    if (!set1.contains(c))
                        break;
                }

            }
        }
        return new String[]{};
    }
}
